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Thread: Azo time

  1. #21

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    Quote Originally Posted by Silverpixels5
    I went to Wal-Mart today and got a 3 dollar clamp light with a 9 inch refletor and a 65 watt plant light. I got the plant light instead of a regular flood light b/c I've heard that azo is more sensitive to blue light and the plant light has an ever so slight blue tint. The light was clipped to my shower curtian rod about 4 feet above my printing frame. This setup cut my times from 5 minutes down to 10-15 seconds, and I've very pleased with the results. Just wanted to give an update, and mention the use of the plant light. :)
    Thanks for sharing your experience with the plant light. Azo is primarily sensitive to light in the near band UV range. It's peak spectral response occurs at 350nm and drops from there to appr. 460 nm. Most of us use reflector floods which have virtually non existant UV outputs and the output from these lamps that is higher then blue is largely wasted. So your plant light is probably much more efficient. The lowest wattage that I have been able to utilize with a reflector flood is 150 watt (Pyrocat HD negatives) and more normally 300 watt (with ABC Pyro negatives).
    I have heard that the more current Azo emulsion is of differing contrast then the earlier emulsion which you indicated that you had. I would be interested in learning your experience with newer emulsion and the plant light. I would appreciate it if you would share your experience in that regard when you have have had time to evaluate it.

  2. #22
    Ed Sukach's Avatar
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    Quote Originally Posted by dnmilikan
    Azo is primarily sensitive to light in the near band UV range. It's peak spectral response occurs at 350nm and drops from there to appr. 460 nm. Most of us use reflector floods which have virtually non existant UV outputs and the output from these lamps that is higher then blue is largely wasted. So your plant light is probably much more efficient.
    A "Sunlamp", used for tanning purposes, might be even more efficient. Their reson for being is UV emanation.
    Carpe erratum!!

    Ed Sukach, FFP.

  3. #23

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    Quote Originally Posted by Ed Sukach

    A "Sunlamp", used for tanning purposes, might be even more efficient. Their reson for being is UV emanation.
    Ed, I agree, the problem is that while Azo is sensitive to UV when purer forms of UV are utilized the paper exposes more rapidly (too rapidly in most cases for effective burning and dodging).

    I have thought that perhaps a lower output UV source might really be beneficial for Azo. The primary reason would be that the proportional stain that Pyro developers impart to the negative act as additional density to blue light and also additionally to UV light as well.

    In the case of blue light the Pyro stain may add the equivalent of appr. .20 units of density at a silver density of 1.20. Effective blue light transmission density then becomes 1.40.

    The proportional stain adds additional density beyond the blue light effect to UV transmission. In the case above, for example, it may add another .20 density units to UV transmission. Effective UV transmission density may then be on the order of 1.55 to 1.60.

    As the negative silver density increases the proportional stain effect to both blue and UV transmission increases.

    The reason that I think that a lower output UV device may be beneficial to Azo users is that it would enable greater expansion of the contrast range of the camera negative then what reflector floods or even plant lamps would enable. Lower contrast films would then perhaps be more useable for Azo. Certainly all films would exhibit the ability to expand density range beyond what the blue light effect alone would be when using proportional staining pyro developers.

    With your experience in this field, Ed, I imagine that you have ideas on how to effect UV usage albeit at a more manageable level. I would appreciate your thoughts on this. Thanks for your input.

  4. #24

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    If you look at Kodak Technical Publication G-10 on AZ0 you will find a spectral sensitivity chart. The direct link is http://www.kodak.com/global/en/profe....44.14.3&lc=en

    As Donald pointed out, AZO is very sensitive to light in the near UV and Violet range, from about 350 to 425 nanometers. One could no doubt expose AZO with the same UV lights that we use with alternative processes such as pt/pd but exposing times would be very short, probably too short to be practical with AZO.

    The plant light seems like a very good idea because these lights put out some UV light but not nearly so much as the lights we use with alternative processes.

    Also, in response to Ed's note about using a sunlamp, it is true that these lamps put out a lot of UV light. However, they appear to have been taken off the market because I have not seen one for sale in years.

    Sandy

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